JavaScript数据结构之单链表和循环链表

数据结构系列前言：

数据结构作为程序员的基本知识，需要我们每个人牢牢掌握。近期我也展开了对数据结构的二次学习，来弥补当年挖的坑。。。。。。当时上课的时候也就是跟着听课，没有亲自实现任何一种数据结构，更别提利用数据结构来解决问题了。现在就来填坑了奋斗在这里提醒看到我博客的孩子们，如果你还是在校生，永远不要轻视任何一门基础课的学习，这个时候挖的坑，要么需要用双倍的努力去填，要么会直接影响一个人的能力等等。。。。。。千万别给自己挖坑

进入正题，关于链表的数据结构知识，这里简单介绍下：

链表是一种物理存储单元上非线性、非连续性的数据结构（它在数据逻辑上是线性的），它的每个节点由两个域组成：数据域和指针域。数据域中存储实际数据，指针域则存储着指针信息，指向链表中的下一个元素或者上一个元素。正是由于指针的存在，链表的存储在物理单元是非连续性的。

链表的优点和缺点同样明显。和线性表相比，链表在添加和删除节点上的效率更高，因为其只需要修改指针信息即可完成操作，而不像线性表（数组）那样需要移动元素。同样的，链表的长度在理论上也是无限的（在存储器容量范围内），并可以动态变化长度，相比线性表优势很大。相应的，由于线性表无法随机访问节点，只能通过指针顺着链表进行遍历查询来访问，故其访问数据元素的效率比较低。

下面是JS部分

这里面封装了的常用方法及描述：

对于各常用方法的算法描述在这里就不写了，相信大家都可以轻易读懂并理解，毕竟都是非常基础的知识了。

单链表：

var length = 0,//存放链表长度
head = null; //头指针

this.append = function(element){
var node = new Node(element),current; //操作所用指针

if (!head){
head = node;
}else {
current = head;

while(current.next){
current = current.next;
}

current.next = node;
}

length++;
return true;
};

this.insert = function(position,element){
if (position >= 0 && position <= length) {
var node = new Node(element),current = head,previous,index = 0;

if(position === 0){
node.next = current;
head = node;
}else{
while(index++ < position){
previous = current;
current = current.next;
}
node.next = current;
previous.next = node;
}

length++;
return true;
}else{
return false;
}
};

this.removeAt = function(position){
if(position > -1 && position < length){
var current = head,index = 0;

if (position === 0) {

head = current.next;

}else{

while (index++ < position){ 
 previous = current; 
 current = current.next; 
} 

previous.next = current.next;

};

length--;
return current.element;
}else{
return null;
}
};

this.remove = function(element){
var current = head,previous;

if(element === current.element){
head = current.next;
length--;
return true;
}
previous = current;
current = current.next;

while(current){
if(element === current.element){
previous.next = current.next;
length--;
return true;
}else{
previous = current;
current = current.next;
}
}
return false;
};

this.remove = function(){
if(length < 1){
return false;
}

var current = head,previous;

if(length == 1){
head = null;
length--;
return current.element;
}

while(current.next !== null){
previous = current;
current = current.next;
}

previous.next = null;
length--;
return current.element;
};

this.indexOf = function(element){
var current = head,index = 0;

while(current){
if(element === current.element){
return index;
}
index++;
current = current.next;
}

return false;
};

this.isEmpty = function(){
return length === 0;
};

this.size = function(){
return length;
};

this.toString = function(){
var current = head,string = '';

while(current){
string += current.element;
current = current.next;
}
return string;
};

this.getHead = function(){
return head;
}

}

循环链表：在单链表的基础上，将尾节点的指针指向头结点，就构成了一个循环链表。环形链表从任意一个节点开始，都可以遍历整个链表。

var length = 0,head = null;

this.append = function(element){
var node = new Node(element),current;

if (!head) {
head = node;
node.next = head;
}else{
current = head;

while(current.next !== head){
current = current.next;
}

current.next = node;
node.next = head;
};

length++;
return true;
};

this.insert = function(position,element){
if(position > -1 && position < length){
var node = new Node(element),index = 0,previous;

if (position === 0) {

node.next = head; 
head = node;

}else{

while(index++ < position){ 
 previous = current; 
 current = current.next; 
} 

previous.next = node; 
node.next = current;

};

length++;
return true;
}else{
return false;
}
};

this.removeAt = function(position){
if(position > -1 && position < length){
var current = head,index = 0;

if (position === 0) {

head = current.next;

}else{

while (index++ < position){ 
 previous = current; 
 current = current.next; 
} 

previous.next = current.next;

};

length--;
return current.element;
}else{
return null;
}
};

this.remove = function (element){
var current = head,indexCheck = 0;

while(current && indexCheck < length){
if(current.element === element){
if(indexCheck == 0){
head = current.next;
length--;
return true;
}else{
previous.next = current.next;
length--;
return true;
}
}else{
previous = current;
current = current.next;
indexCheck++;
}
}
return false;
};